In wood shearing machine having the wood supporting table with a supporting surface which is vertical or slightly inclined to the vertical, the traversing device of the whole assembly comprising the blade-holding unit and the bar-carrying unit, usually consisting of a pair of screws connecting the two slides forming the side shoulders of the blade-holding unit and bar-carrying unit, with two rear reaction bodies integral with the bed of the wood shearing machine and placed at its end. The means actuating said screws may vary and do not form part of the present invention.
The function of the screws is to allow the bar-carrying unit and the blade-holding unit to readily come close to the wood stock to be cut before the actual cutting of the wood takes place, and in addition to move the unit forwardly an amount each time, equal to the thickness of the sheets cut as these are obtained.
Every time an operation is undertaken to act upon the blade and the wood stock, or a new wood stock has to be loaded, the screws allow the bar-carrying unit and the blade-holding unit to readily move away towards the rear reaction bodies. Said movements being enabled by rotating the screws in one direction or the other and the screws are connected together by suitable mechanical means so that the slides move forward or rearward accordingly.
Such known solution has a serious drawback due to the fact that the action of the screws is performed on a horizontal plane or a plane slightly inclined to the horizontal, which is relatively distant from the point where the blade and the pressure bar come into contact with the wood stock.
The pressure bar has therefore a pressing force on the wood stock which is in the same direction but is separate from the force imparted by the screws on the blade-holding unit and the bar-carrying unit with the result that torques are generated which tend to rotate the assembly comprising the blade-holding unit and the bar-carrying unit overcoming its force of gravity and causing it to move away from its supporting surface with the obvious result of a faulty and uneven operation.